<!DOCTYPE html>
<html>
    <head>
        <script src="js/vue.js"></script>
        <style>
            /* .row-enter{
                width: 0px;
            }

            .row-enter-to {
                width: 200px;
            }

            .row-enter-active {
                transition: width 3s;
            } */

            .red {
                background: red;
                height: 20px;
            }

            .blue {
                background: blue;
                height: 20px;
            }

            .yellow {
                background: yellow;
                height: 20px;
            }

        </style>
    </head>
    <body>
        <div id="app">
            <button @click="showNum">切换</button>
            <transition name="row">
                <div class="red" v-if="show=='A'" key="A"></div>
                <div class="blue" v-if="show=='B'" key="B"></div>
                <div class="yellow" v-if="show=='C'" key="C"></div>
            </transition>
        </div>
        <script>
            var vm = new Vue({
                el:'#app',
                data : {
                    show : 'A'
                },
                methods : {
                    showNum() {
                        if(this.show == 'A'){
                            this.show = 'B';
                        }
                        else if (this.show == 'B') {
                            this.show = 'C';
                        }
                        else {
                            this.show = 'A';
                        }
                    }
                }
            });
        </script>
    </body>
</html>